The present invention relates to a method for manufacturing an embossed can body where a pattern is printed on an outer surface of a cylindrical can barrel, and one or both of a projection portion and a recess portion are registered with the pattern and are formed on at least one portion of the pattern, in particular, a method for manufacturing an embossed can body which can perform an alignment between a pattern and at least one portion of a projection portion and a recess portion (a projection portion/a recess portion) securely.
In recent years, because of variety in design, improvement in strength of a can barrel according to thinning a wall thickness of a can barrel, and the like, an embossed can body whose can barrel has been subjected to one or both of projecting working and recessing working is developed and commercialized.
In this case, when one or both of projecting work and recessing work are performed on the embossed can body with alignment with a pattern, a character or the like (which are collectively referred to as pattern) which has been printed on the embossed can body, a design performance of the embossed can body can be improved. For this reason, an embossing of one or both of a recess portion and a projection portion corresponding to a pattern is performed on at least one portion of the pattern.
FIG. 12 is a perspective view of one example of an embossed can body.
An embossed can body 10 shown in FIG. 12 is a three piece can comprising a can barrel 11xe2x80x2, a can lid 12 and a can bottom 13. The can barrel 11xe2x80x2 is made of a metal thin plate, and is formed in a cylindrical shape by welding both ends of the thin plate at welding portions 14.
Printed at an upper portion on an outer surface of the can barrel 11xe2x80x2 is a pattern (characters) 11d which is xe2x80x9cBEERxe2x80x9d. Also, a pattern (characters) 15 which is xe2x80x9cCANxe2x80x9d and which is worked to be recessed or projected is largely printed at a central portion of the outer surface of the can barrel.
The patterns 11d, 15 are covered with a polyester film or an organic coating after they are printed on the outer surface of the can barrel 11xe2x80x2. The patterns may be printed on a back surface (a surface contacting with an outer surface of the can barrel) of the polyester film or the organic coating in advance.
Recess portions 16 which correspond to xe2x80x9cCANxe2x80x9d are formed on the can body 11xe2x80x2 in a state where they are aligned with the pattern 15. In an aspect where the forming is performed in the state where the pattern 15 and the recess portions 16 correspond to each other, it is not limited to an aspect where the entire pattern corresponds to the entire recess portions. An aspect where the pattern 15 corresponds to a portion of the recess 16 may be allowed. For example, an aspect where recessing is performed on only xe2x80x9cAxe2x80x9d of the pattern xe2x80x9cCANxe2x80x9d or printing is performed on xe2x80x9cAxe2x80x9d of the recess portion xe2x80x9cCANxe2x80x9d may be possible.
As conventional techniques for performing such one or both of a recess portion and a projection portion forming work on a can barrel, there have been known the title xe2x80x9cTOOLING AND METHOD THE EMBOSSING OF A CONTAINER AND THE RESULTING CONTAINERxe2x80x9d of International Laid-Open Publication No. WO98/03279 and the title xe2x80x9cMETHOD OF ORIENTING CANSxe2x80x9d of No. WO97/21505.
In these conventional techniques, a positioning mark 17 indicating a position of a pattern portion is formed on the can barrel 11xe2x80x2 in order to position forming means for performing one or both of a recess portion and a projection portion forming work to the pattern portion of the can barrel, as shown with a can body 10 in FIG. 12 and the mark 17 is read by a sensor, so that the rotation of the can barrel 11xe2x80x2 is controlled such that the pattern 15 is positioned so as to correspond to the forming means.
Also, for the purpose of reducing manufacturing cost of a can body, a rotary type apparatus and a method for performing recess and projection working at a high speed have been disclosed, for example, in International Laid-Open Publication Nos. WO98/03279 and WO98/03280.
FIG. 13 is a diagram explaining procedures for performing recess and projection working on the can barrel 11xe2x80x2 by the above rotary type apparatus and method.
The can barrel 11xe2x80x2 is introduced from a position shown with (1) in FIG. 13. The positioning mark 17 (refer to FIG. 12) of the introduced can barrel 11xe2x80x2 is detected at turret positions (1) and (2) by sensors 151 or the like arranged at respective pockets.
The sensors 151 or the like detect the mark 17. The can barrel 11xe2x80x2 is rotated such that the pattern 15 faces a predetermined position (a position which corresponds to recess/projection portion of a forming die). Thereafter, while the attitude of the can barrel 11xe2x80x2 is maintained, the can barrel 11xe2x80x2 is sent up to a position shown with a turret position (3) in FIG. 13 where an inner roller 101 is inserted.
Also, a cam member 140 is disposed outside the inner roller 101 over a range slightly larger than a range of a turret positions (3) to (9). The cam member 140 shifts the outer roller 102 towards the inner rollers 101 by means of a cam roller (not shown). Thereby, an inner wall of the can barrel 11xe2x80x2 positioned so as to contact the outer roller 102 is pressed on to the inner roller 101 in the range of the turret positions (4) to (8).
Then, a recess/projection working is performed on the can barrel 11xe2x80x2 while the inner roller 101 and the outer roller 102 are being rotated in the range of the turret positions (4) to (8). When the can barrel 11xe2x80x2 is fed up to the turret position (9), the pressing of the cam roller (not shown) effected by the cam member 140 is released, and the inner roller 101 comes out from the can barrel 11xe2x80x2.
In this manner, the working for the recess portion 16 is performed on the pattern 15 of the can barrel 11xe2x80x2. The can barrel 11xe2x80x2 which has been worked is conveyed out at an discharging position A from the forming apparatus of the can body.
These conventional techniques are excellent inventions, but there are drawbacks to be improved in view of implementation thereof.
That is, in a case that embossing is performed at a high speed of 1,000 cans to 2,000 cans/min., when there is variation in shape of can barrels 11xe2x80x2 such as circularity or the like, there occurs a case where the sensors 151 can not read the positioning mark 17 of the can barrel 11xe2x80x2 accurately because the can barrel 11xe2x80x2 is rotated at high speed. As a result, it becomes impossible to perform an accurate positioning so that the pattern 15 and the recess portion 16 do not correspond to each other in some cases.
Also, in can manufacturing steps, there occurs a case where the can barrel 11xe2x80x2 becomes dirty or dusts stick to the can barrel 11xe2x80x2. In such a case, there is a case that the sensors 151 mistake dirt for the positioning mark 17. Particularly, in a can body which has the can barrel 11xe2x80x2 having a metallic welded line such as a three piece can, there is a case where the sensors 151 mistake a welded portion for the positioning mark 17.
Furthermore, in a case that there are variations in shape of the can barrel 11xe2x80x2, when the can barrel 11xe2x80x2 sets to the inner rollers 101 which is a forming die for performing embossing, the set position of the can barrel 11xe2x80x2 varies. As a result, there is a problem that embossing corresponding to the pattern 15 can not be performed securely.
Also, even if the orientation of the can barrel 11xe2x80x2 is adjusted according to the positioning mark 17 before forming, when slippage occurs between the outer roller 102 and the can barrel 11xe2x80x2, the pattern 15 and the recess portion 16 deviate from each other, thereby resulting in a poor product.
On the other hand, in order to inspect the pattern 15 and the recess portion 16 after formation, it is sufficient to detect by the sensors 151 provided in respective pots whether or not the positioning mark 17 is directed to a predetermined direction. However, when the outer rollers 102 are separated from the can barrel 11xe2x80x2, there is a case that slippage between the can barrel 11xe2x80x2 and the outer roller 102 occurs and the can barrel 11xe2x80x2 rotates. In such a case, there is a drawback that, even when a product is a good one, it may be judged as a bad product erroneously.
These problems occur in an embossed can body of a two piece can like the above.
An object of the present invention is to obtain embossed can bodies having a high quality where a pattern and an embossing coincide with each other with a very high accuracy in a stable manner by solving the these problems.
A method for manufacturing an embossed can body of the present invention is a method for manufacturing an embossed can body where a pattern is printed on an outer surface of a cylindrical can barrel, alignment with the pattern is performed, and embossing of one or both of a recess portion and a projection portion is performed on at least one portion of the pattern, wherein a plastic working step for performing plastic working on one portion of a periphery of the can barrel to form a plastically deformed portion is provided prior to an embossing step for performing the alignment with the pattern to perform embossing of one or both of the recess portion and the projection portion on the pattern.
In the plastic working step, it is preferable that a neck portion and a flange portion are formed at an opening edge portion of the can barrel by the plastic working. Also, it is preferable to perform the alignment of the pattern and one or both of the recess portion and the projection portion by detecting a plurality of positioning marks provided on the pattern or a portion except for the pattern.
An inspecting apparatus of the present invention is an inspecting apparatus for a can body which is provided in a forming apparatus for a can body, the forming apparatus including one die on which a can barrel is mounted and the other die aligned with a pattern which has been printed on an outer surface of the can barrel to perform recess/projection working on at least one portion of the pattern of the can barrel, and which inspects whether or not the pattern and the worked recess and/or projection are aligned with each other, comprising: a camera positioned at a predetermined position and photographing the can body during a recess/projection working; inspecting timing detecting means for detecting a predetermined timing for inspection during the recess/projection working; image processing means for processing an image which has been photographed by the camera; and judging means for comparing an extraction pattern which has been taken out from the pattern and a reference pattern which has been set in advance with each other on the basis of the process result of the image processing means to set a first reference position at a predetermined position on the basis of the pattern when the extraction pattern and the reference pattern are identical and to obtain a distance between the first reference position and a second reference position which has been set at a predetermined position and for judging whether or not the distance between the first reference position and the second reference position is in an allowable range of a distance which has been set in advance.
It is preferable to set the first reference position to the position of the extraction pattern.
An inspecting method of the present invention is an inspecting method for a can body where the can body is mounted to one die, the other die is aligned with a pattern which has been printed on an outer surface of a barrel of the can body, and when a recess/projection working is performed on at least one portion of the pattern by the one die and the other die, inspection is made about whether or not the pattern and the worked recess/projection have been aligned with each other, comprising: the step of photographing at least one portion of the can body during a recess/projection working by a camera which has been positioned at a predetermined position; the step of extracting at least one portion of the pattern from an image which has been photographed by the camera at a predetermined timing during the recess/projection working; the step of setting a first reference position on the basis of the position of the extracted pattern when it is judged that one portion of the extracted pattern is identical to a reference pattern which has been set in advance; the step of photographing a mark which has been provided in advance together with the can body by the camera and setting the second reference position on the basis of the position of the mark when it is judged that the mark exists at a predetermined position in an image which has been photographed by the camera; and the step of obtaining the distance between the first reference position and the second reference position to judge whether or not the distance is in an allowable range of distance which has been determined in advance.